Coulomb’s law & electric fields worksheet with answers

Free printable Coulomb’s law & electric fields worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
−−8 µC−−8 µCr = 3 cm

Two point charges of −8 µC and −8 µC are 3 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −8 µCq2 = −8 µCr = 3 cm
F = N
2.Easy
+ + + + + +− − − − − −e⁻E = 2700 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 2700 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 2700 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
3.Medium
++8 µC++2 µCP40 cm

A charge of +8 µC and a charge of +2 µC are 40 cm apart. Point P lies on the line between them, 10 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +8 µCq2 = +2 µCr1 = 10 cmr2 = 30 cm
E = N/C
4.Medium
++2 µC++3 µCE = 010 cm

Charges of +2 µC and +3 µC are 10 cm apart. At what distance x from the +2 µC charge, on the line between them, is the electric field zero?

q1 = +2 µCq2 = +3 µCd = 10 cm
x = cm
5.Hard
3 cm8 cm+q1​ = +2 µC+q3​ = +3 µC+q2​ = +4 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 3 µC is at the right-angle corner, q₁ = 2 µC is 3 cm from it along one side and q₂ = 4 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 4 µCq3 = 3 µCr13 = 3 cmr23 = 8 cm
F = N
6.Hard
5 cm5 cm+q1​ = +1 µC+q3​ = +1 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 1 µC is 5 cm from it along one side and q₂ = 10 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 1 µCq2 = 10 µCq3 = 1 µCr13 = 5 cmr23 = 5 cm
F = N

Answer key

  1. 1. F = 639.3 N
  2. 2. a = 4.748 × 10¹⁴ m/s²
  3. 3. E = 6.992 × 10⁶ N/C
  4. 4. x = 4.495 cm
  5. 5. F = 62.26 N
  6. 6. F = 36.14 N

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